水稻回交世代中两个抗纹枯病主效数量基因的鉴定与标记辅助选择

Identification and Marker-assisted Selection of Two Major Quantitative Genes Controlling Rice Sheath Blight Resistance in Backcross Generations

对水稻品种特青与Lemont杂交组合的F2 单株无性系群体,进行 2年有重复的抗水稻纹枯病QTLs定位,在特青的第 9号染色体和Lemont的第 11号染色体上分别定位到了 1个主效抗纹枯病QTL,各自命名为qSB 9和qSB 11。从该F2 定位群体中,根据位点双侧标记带型,选取 2个位点均为感病等位基因纯合的 2个单株作为双感亲本,均为抗病等位基因纯合的 1个单株作为双抗亲本,分别与轮回亲本特青和Lemont进行回交。标记辅助选择始于BC2F1 及以后的各回交世代,并于BC2F1 和BC4F1 世代进行了病原菌人工接种鉴定。鉴定结果表明,qSB 9和qSB 11确实存在于原定位区间,各等位基因也在回交过程中被成功选择。BC3F2 采用秧田期大群体标记检测,从中选取符合要求的单株,分别混合得到特青背景下的双感纯合系, Lemont背景下的双感、双抗纯合系,将这些纯合系连同轮回亲本同时种植于扬州大学农学院试验田和江苏里下河农科所试验田, 2次重复,随机区组设计,进行接种实验。结果表明: 1 )相同背景下的不同纯合系间在发病程度上存在极显著的差异,不同纯合系的病情严重程度依次为:Lemont双感系>特青双感系>Lemont>特青 >Lemont双抗系; 2 )2个位点上的抗性等位基因qSB 9和qSB 11单独存在时,分别可减轻病级 1 2级左右,同时存在时可减轻病级 2级左右;

We constructed an F_2 clonal population of intercross,Teqing/Lemont,and identified two quantitative trait loci (QTLs) contributing to rice sheath blight resistance on chromosome 9 and 11.The two QTLs were qSB-9 and qSB-11,respectively.From the population,three clonal lines were selected by markers’ band types on both sides of these two QTLs,qSB-9 and qSB-11.Two were double-susceptible parent with homozygous susceptible alleles of these two loci,and the other was named as double-resistant parent,of which these two loci were all homozygous resistant alleles.These parents were separately backcrossed to recurrent parents,Teqing or Lemont.From BC_2F_1,marker-assisted selection was conducted in each proceeding generation and all backcrossed plants in BC_2F_1 and BC_4F_1 were inoculated by short toothpicks incubated with a strain,RH-9 of the fungus for identification of the resistance.Results suggested that these two QTLs were selected effectively in each backcross generation and their positions were also verified in identification of resistance to rice sheath blight. In seedling nursery of BC_3F_2 population,plants were selected through marker-assisted selection,and were separately mixed as homozygous lines of double-susceptible alleles on the background of Teqing,double-susceptible and double-resistant on the background of Lemont.The homozygous lines and their recurrent parents were simultaneously planted on experiment fields of Agriculture Collage of Yangzhou University and Lixiahe District Institute of Agricultural Science.The inoculation was performed by a random-block test with two replicates at each site.The results indicated that 1) The difference of sheath blight disease development was highly significant (among) materials under the same genetic background,and the order of disease seriousness among different homozygous lines were: double-susceptible line on the background of Lemont > double-susceptible line on the background of Teqing > Lemont > Teqing > double-resistant line on the background of Lemont; 2) When the resistant allele of qSB-9 or qSB-11 solely existed in a plant,its disease rating was reduced about 1.2 score,and 2.0 score when they simultaneously existed on the background of Lemont; 3) No significant interaction between the two QTLs controlling sheath blight resistance and environments was found.These studies have laid a strong groundwork in operation and application of these QTLs contributing to rice sheath blight resistance.